Mapping JSON Result to an Enum in Swift

What you need is a custom encoder and decoder. Another issue in your code is that you are not specifying the integer value of your enumeration cases which should start with 1 (if you don’t specify it will start with zero). So your enumeration should look like this:

enum Role: Int, Codable, Identifiable {
    case student = 1, faculty
    var id: RawValue { rawValue }
    private enum CodingKeys: String, CodingKey {
        case id, name
    }
}

Then you can create a custom decoder:

extension Role {
    public init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        let id = try container.decode(Int.self, forKey: .id)
        let name = try container.decode(String.self, forKey: .name)
        switch (id, name) {
        case (1, "Student"):
            self = .student
        case (2, "Faculty"):
            self = .faculty
        default:
            throw DecodingError.dataCorrupted(
                .init(
                    codingPath: decoder.codingPath,
                    debugDescription: "Invalid Role data"
                )
            )
        }
    }
}

And if you need to encode it as well a custom encoder:

extension Role {
    public func encode(to encoder: Encoder) throws {
        var container = encoder.container(keyedBy: CodingKeys.self)
        try container.encode(id, forKey: .id)
        switch self {
        case .student:
            try container.encode("Student", forKey: .name)
        case .faculty:
            try container.encode("Faculty", forKey: .name)
        }
    }
}

Playground testing:

let jsonData = Data(#"[{"id":1,"name":"Student"},{"id":2,"name":"Faculty"}]"#.utf8)
let roles: [Role] = [
    .init(rawValue: 1)!,
    .init(rawValue: 2)!
]
let encodedRoles = try JSONEncoder().encode(roles)
print(encodedRoles == jsonData)  // "truen"
do {
    let decodedRoles = try JSONDecoder().decode([Role].self, from: jsonData)
    print(roles == decodedRoles)    // "truen"
} catch {
    print(error)
}